Byzantium and the Arabs.—On the partition of the Roman Empire in 395 A.D., Palestine fell naturally to the eastern or Byzantine half, but it was not long before the growing power of Persia menaced the hold of the Byzantine Emperors on the Holy Land. In 614 Jerusalem fell to Chosroes II. after a siege of twenty days, and its treasures were plundered. The Emperor Heraclius subsequently recovered the country; but in the struggles with the Persians the Byzantine Empire underwent a process of exhaustion which accounts very largely for its subsequent collapse before the Arab invaders.
The Arab Conquest.—The Arabs had from time immemorial ranged over the vast Syrian Plain as far as Mesopotamia, and were now beginning to press forward into Syria and Palestine. The southern Arabs (Yoqtanids or Qahtanids) settled in the Hauran, while opposed to them were the tribes of Northern Arabia (Ishmaelites); but these tribes acquired a new significance after their union had been effected by the Prophet Mohammed. As the Byzantine Empire grew weaker, the raids of these Arabs into Palestine became more frequent. Finally they took the definite shape of deliberate conquest. The invasion began in the south of Palestine, where the local Governor, Sergius, operating from Caesarea, was defeated early in 634. This Arab victory was followed up by another in the same year, when Theodore, the brother of Heraclius, was defeated in the Wadi al-Sant. Further victories were won by the Arabs in 635, and in September of that year Damascus surrendered. Heraclius now made his one great effort to save Syria. In the summer of 636 an army of imperial mercenaries and Armenians and Arabs (drawn from the settled tribes of Syria) advanced through the Biqaʾ and past Baniyas and across the Jordan, south of Lake Huleh. They cut the communication between Damascus and Arabia. But the Arabs had already abandoned Damascus and had taken their position on a strong line of defence, just south of the River Yarmuk. The opposing armies seem to have faced one another on opposite
